A border gateway protocol (BGP) is an inter-autonomous system (AS) dynamic routing protocol, which is not aimed to discover or calculate a route, but to control route propagation and select an optimal route, i.e., to automatically exchange loop-free AS path reachability information among the ASs, so as to construct a topology of an autonomous region, thereby eliminating the routing loops. Here, an AS is defined as a set of routers under the same technical administration and using the same routing policy. For example, FIG. 1 is a schematic view of a BGP network in the conventional art. In the BGP network shown in FIG. 1, an AS A has two loop-free routes to an AS D, which are that the AS A reaches the AS D via an AS C, and the AS A reaches the AS D via an AS E. The AS A selects an optimal route, for example, the loop-free route passing through the AS C, and notifies the optimal route to the AS C in the process of inter-AS route exchange.
As the Internet has become the bearer network of more and more services, increasingly high reliability of the Internet is required. Being a routing protocol among ASs in the Internet, the robustness of the BGP greatly affects the reliability indices of the Internet. For example, in the BGP network shown in FIG. 1, the AS A and the AS B both need to reach the AS D via the AS C, and the AS A also has a sub-optimal route passing through the AS E in addition to the optimal route through the AS C. However, according to a transmission method based on the BGP, the AS C cannot obtain information about the sub-optimal route. Once the path between the AS C and the AS D fails, i.e., the network topology changes, the routing protocol between the ASs needs to recalculate the routes that reflect the latest topology, which is called a “convergence” process. In the process of waiting for the convergence, the AS C may discard data packets sent from the AS A and the AS B till a new route is discovered after the convergence process is completed. For example, if the discovered new route is the sub-optimal route passing through the AS E, the AS C and the AS B respectively transmit data packets to the AS D via the AS A and the AS E. It can be seen that the data packets sent to the AS C whose destination is the AS D are discarded in the process of waiting for the convergence, thus resulting in a flow interruption.
In order to solve the problem of temporary flow interruption occurring in the process of waiting for the BGP convergence, in a resilient BGP (RBGP) method, the AS A notifies the pre-calculated sub-optimal route to the AS C as a standby route. In this manner, when the connection between the AS C and the AS D is interrupted, the AS C forwards the data packets whose destination is the AS D to the AS A via the standby route, and then the AS A transmits the data packets to the AS D via the AS E. As such, in the process of waiting for the BGP convergence, the data packets are forwarded via the pre-calculated standby route, and thus the flow will not be interrupted.
However, as the BGP convergence generally lasts for several seconds, there is not enough time for the convergence of routers within the AS A in the convergence process, i.e., the router within the AS A still uses the AS C as a next-hop AS to the AS D. If the AS A fails to identify that the data packets need to be forwarded via the sub-optimal route, the data packets will be forwarded to the AS C again, so that a loop is formed between the AS C and the ASA.
Seen from the above analysis, in the current transmission method based on the BGP, the BGP network is still not robust enough for the transmission of the data packets, and the transmission performance based on the BGP is poor.